Curcumin reduces the toxic effects of iron loading in rat liver epithelial cells.

BACKGROUND/AIMS: Iron overload can cause liver toxicity and increase the risk of liver failure or hepatocellular carcinoma in humans. Curcumin (diferuloylmethane), a component of the food spice turmeric, has antioxidant, iron binding and hepatoprotective properties. The aim of this study was to quantify its effects on iron overload and the resulting downstream toxic effects in cultured T51B rat liver epithelial cells. METHODS: T51B cells were loaded with ferric ammonium citrate (FAC) with or without the iron delivery agent 8-hydroxyquinoline. Cytotoxicity was measured by methylthiazolyldiphenyl-tetrazolium bromide assay. Iron uptake and iron bioavailability were documented by chemical assay, quench of calcein fluorescence and ferritin induction. Reactive oxygen species (ROS) were measured by a fluorescence assay using 2',7'-dichlorodihydrofluorescein diacetate. Oxidative stress signalling to jnk, c-jun and p38 was measured by a Western blot with phospho-specific antibodies. RESULTS: Curcumin bound iron, but did not block iron uptake or bioavailability in T51B cells given FAC. However, it reduced cytotoxicity, blocked the generation of ROS and eliminated signalling to cellular stress pathways caused by iron. Inhibition was observed over a wide range of FAC concentrations (50-500 microM), with an apparent IC(50) in all cases between 5 and 10 microM curcumin. In contrast, desferoxamine blocked both iron uptake and toxic effects of iron at concentrations that depended on the FAC concentration. The effects of curcumin also differed from those of alpha-tocopherol, which did not bind iron and was less effective at blocking iron-stimulated ROS generation. CONCLUSIONS: Curcumin reduced iron-dependent oxidative stress and iron toxicity in T51B cells without blocking iron uptake.

Cytotoxic effect of oyster mushroom Pleurotus ostreatus on human androgen-independent prostate cancer PC-3 cells.

Twenty species of edible mushrooms and three purified mushroom polysaccharides were screened for their antitumor potential on human androgen-independent cancer PC-3 cells. A water-soluble extract (POE) prepared from the fresh oyster mushroom Pleurotus ostreatus produced the most significant cytotoxicity on PC-3 cells among the mushroom species tested. At the same time, POE induced a rapid apoptosis on PC-3 cells detected with annexin V-fluorescein isothiocyanate flow cytometry when the cells were exposed to POE (150 microg/mL) for 2 hours. Induced apoptosis was also confirmed by DNA fragment terminal deoxynucleotidyl transferase-mediated X-dUTP nick end labeling staining while POE (200 microg/mL) was added to PC-3 cells for 6 hours. Both cytotoxicity and induced apoptosis mediated by POE in PC-3 cells are dose-dependent. Interestingly, PC-3 cells appeared to be more sensitive to POE in anchorage-independent growth condition. Tumor colony-forming efficiency was dramatically reduced to 4.5% or 0.5% in POE (60 or 120 microg/mL)-supplemented soft agar medium compared with that of POE-free medium (defined as 100%). Temperature in POE processing plays a decisive role for the cytotoxic activity. Bioactivity of POE was eliminated by exposure to high temperature (80 degrees C) for 2 hours; however, it remained stable at a series temperatures of below 40 degrees C. The active fraction POE-F2 was analyzed and identified by size exclusion of high performance liquid chromatography and the CellTiter 96 AQueous Cell Proliferation Assay (Promega, Madison, WI). Since POE-F2 is also sensitive to heat and has strong 280 nm absorption, the results imply that active compounds recovered from P. ostreatus are water-soluble proteins or polypeptides.